Mechanism of photocatalytic water splitting with triazine-based carbon nitrides: insights from ab initio calculations for the triazine-water complex

Polymeric carbon-nitride materials consisting of triazine or heptazine units have recently attracted vast interest as photocatalysts for water splitting with visible light. Adopting the hydrogen-bonded triazine-water complex as a model system, we explored the photochemical reaction mechanisms involv...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2018, Vol.20 (21), p.14420-14430
Main Authors: Ehrmaier, Johannes, Janicki, Mikołaj J, Sobolewski, Andrzej L, Domcke, Wolfgang
Format: Article
Language:English
Subjects:
Carbon
Chemical bonds
Decomposition reactions
Electronic structure
Hydrogen
Hydrogen bonding
Hydroxyl radicals
Molecular chains
Nitrides
Oxidation
Photocatalysis
Photochemical reactions
Reaction mechanisms
Water splitting
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Summary:Polymeric carbon-nitride materials consisting of triazine or heptazine units have recently attracted vast interest as photocatalysts for water splitting with visible light. Adopting the hydrogen-bonded triazine-water complex as a model system, we explored the photochemical reaction mechanisms involved in the water splitting reaction in this system, using wavefunction-based ab initio electronic-structure methods. It is shown that photoexcited triazine can abstract a hydrogen atom from the water molecule by the sequential transfer of an electron and a proton from water to triazine, resulting in the triazinyl-hydroxyl biradical in the electronic ground state. It is furthermore shown that the excess hydrogen atom of the triazinyl radical can be photodetached by a second photon, which regenerates the triazine molecule. The hydrogen-bonded water molecule is thus decomposed into hydrogen and hydroxyl radicals in a biphotonic photochemical reaction. These results shed light on the molecular mechanisms of the water-oxidation reaction catalyzed by triazine-based organic polymers.
ISSN:1463-9076
1463-9084
DOI:10.1039/c8cp01998c